1. Field of the Invention
The field of endeavor relates generally to medical devices and methods. More particularly, the filed of endeavor relates to medical devices and methods for infusing therapeutic agents into a body lumen, such as a blood vessel, for treating disorders or conditions present in the body lumen, such as dissolving and disrupting occlusive materials from the blood vessel wall.
2. Description of Related Art
Thrombosis and atherosclerosis are common ailments which occur in humans and which result from the deposition of thrombus within the lumen of blood vessels. When hardened, such deposits are commonly referred to as plaque or clots. Such deposits are common in the peripheral blood vessels that feed the limbs of the human body and the coronary arteries which feed the heart. Stasis, incompetent valves, and trauma in the venous circulation can cause thrombosis, particularly occurring as a deep vein thrombosis in the peripheral vasculature. When such deposits accumulate in localized regions of the blood vessel, they can restrict blood flow and cause a serious health risk. Thrombosis can develop in cerebral vessels, as well, and be the source of ischemic strokes.
In addition to forming in the natural vasculature, thrombosis is a serious problem in “artificial” blood vessels, particularly in peripheral femoral-popliteal and coronary bypass grafts and dialysis access grafts and fistulas. The creation of such artificial blood vessels requires anastomotic attachment at at least one, and usually at least two, locations in the vasculature. Such sites of an anastomotic attachment are particularly susceptible to thrombus formation due to narrowing caused by intimal hyperplasia, and thrombus formation at these sites is a frequent cause of failure of the implanted graft or fistula. The arterio-venous grafts and fistulas which are used for dialysis access are significantly compromised by thrombosis at the sites of anastomotic attachment and elsewhere. Thrombosis often occurs to such an extent that the graft needs to be replaced within a few years or, in the worst cases, a few months.
A variety of methods have been developed for treating thrombosis and atherosclerosis in the coronary and peripheral vasculature as well as in implanted grafts and fistulas. Such techniques include surgical procedures, such as coronary artery bypass grafting, and minimally invasive procedures, such as angioplasty, atherectomy, thrombectomy, thrombolysis, transmyocardial revasculaturization, and the like.
A variety of techniques have been developed for dissolving clots using thrombolytic agents, such as tissue plasminogen activator (tPA), streptokinase, urokinase, and the like. Thrombolytic agents can be very effective at attacking and dissolving relatively soft clots, such as that formed in deep veins. Such agents, however, require time to act, and local delivery catheters often employ isolation balloons to provide high local concentrations of the active thrombolytic agents. Even with such enhanced concentrations, the agents can take extended periods to act, rendering the treatments lengthy and inefficient. In some instances, extensive regions of clot simply cannot be effectively treated using thrombolytic agents alone. In such cases, it has been further proposed to provide a mechanical element to disrupt the clot while the thrombolytic agents are being delivered. An example of such a mechanical approach is disclosed, for example, in U.S. Pat. No. 5,947,985 to Mir A. Imran which describes a catheter having axially spaced-apart balloons for isolating a treatment region within a blood vessel. The catheter also includes a port for delivering thrombolytic agent between the spaced-apart balloons and a helical wire for removing clot material from the blood vessel wall to assist in aspiration.
As will be appreciated from the foregoing, it is known that because of blood flow through blood vessels, drugs and therapeutic agents delivered to the site of an angioplasty procedure, for example, can be rapidly dissipated and removed from the delivery site before they can be absorbed in sufficient quantities to become effective. Catheters have therefore been developed to directly deliver drugs to the desired site and maintain the drugs there. In some cases, the treatment catheter includes delivery ports or other structures that bear against the occluded site within the blood vessel and conduct a thrombolytic agent directly to the occluded site as disclosed in U.S. Pat. No. 5,904,670 to Schreiner. U.S. Pat. No. 6,280,413 to Clark et al. discloses a thrombolytic agent and drug delivery catheter with an expanding portion which is adapted to bear against and deliver the thrombolytic agent directly to the occluded site.
U.S. Pat. No. 5,087,244 to Wolinsky et al. discloses a catheter with a flexible balloon having a plurality of minute openings. The balloon can be inflated by heparin. As the wall of the balloon contacts the arterial wall, the heparin exits the balloon, directly on the walls. However, the balloon can block the perfusion of blood distal to the delivery site, depriving downstream tissue of needed blood. This limits the amount of time available for drug delivery. The inflation of the balloon can also damage the arterial wall, promoting restenosis. In addition, since the balloon is inflated by the heparin, heparin can leak out before the arterial wall is contacted, wasting the drug. The balloon further needs to be deflated prior to removal or to allow blood flow. The pressure required to deflate the balloon could also draw blood into the balloon, preventing further use of the catheter until the blood has been removed. U.S. Pat. No. 4,824,436, also to Wolinsky, discloses a drug delivery catheter comprising a pair of occlusion balloons for securing the catheter in position and isolating a region of the artery which has been opened by percutaneous translumenal coronary angioplasty (PTCA), and a drug delivery conduit for delivering heparin under pressure into the region isolated by the occlusion balloons. The pressure of the heparin forces the heparin to coat and penetrate the arterial tissue. This configuration presents similar perfusion problems to those discussed previously in connection with U.S. Pat. No. 5,087,244 to Wolinsky et al. The heparin, therefore, is only delivered for about 5-60 seconds which may be inadequate for sufficient absorption. U.S. Pat. No. 5,336,178 to Kaplan et al. discloses a catheter with drug delivery ribs which are brought into contact with the walls of the blood vessel lumen by an inflatable balloon. A series of ports in the catheter shaft are provided proximal to the balloon to allow for perfusion of blood through the catheter shaft.
Due to the possibility of damaging the blood vessel wall, other devices (i.e., catheters) combine the ability to deliver or infuse a thrombolytic agent with simple agitation within the blood vessel to remove the thrombus and thus avoid inflatable balloon type delivery systems. U.S. Pat. No. 6,663,613 to Evans et al. discloses a catheter which combines the ability to deliver or infuse a thrombolytic agent into a blood vessel with an agitation action which mechanically disrupts the clot forming the occlusion in the blood vessel. Another patent, U.S. Pat. No. 6,936,025 to Evans et al., combines the delivery of a lysing agent to a blood vessel with a low frequency vibration motion of the catheter body to achieve clot dislocation/disruption.
It is well-known that if a portion of the thrombus separates from the blood vessel wall and is transported through the cardiovascular system, it can cause an embolism, or blockage of a blood vessel. A thrombus in a deep vein in the leg can cause a pulmonary embolism. A thrombus in a coronary artery can cause myocardial infarction. Similarly, a thrombus in a cerebral artery can cause cerebral infarction (i.e., ischemic stroke). As a result, devices have been developed which attempt to filter dislodged thrombus or thrombotic material during therapeutic procedures such as the delivery of thrombolytic agents to a blood vessel to minimize the chance of a dislodged thrombus causing significant damage to the patient. A typical form of these devices is as a filter “net” which intercepts the dislodged thrombus or thrombotic material is disclosed in U.S. Pat. No. 6,053,932 to Daniel et al. which discloses an emboli capturing system adapted to catch emboli in blood vessels. This patent discloses a microporous mesh formed of woven or braided fibers or wires, or a microporous membrane, for capturing the dislodged emboli/thrombus. Another such filter “net” is disclosed in U.S. Patent Application Publication No. 2003/0199819 to Beck, which discloses a balloon catheter with downstream “safety net” that prevents any dislodged material from migrating through a patient's bloodstream. Often, “net” type devices are used in combination with a catheter having a suction capability such that dislodged thrombus is sucked into a lumen in the catheter with the mesh or net structure provided mainly for redundant safety purposes. Such a catheter having suction capability is disclosed in U.S. Pat. No. 6,805,692 to Muni et al. One known catheter apparatus includes multiple infusion ports for delivering a thrombolytic agent to a blood vessel with several of the infusion ports provided within a filter basket for delivering the thrombolytic agent in the area defined by the filter basket to dissolve any dislodged thrombus trapped in the filter, (See U.S. Pat. Nos. 6,755,813 and 6,749,619 to Ouriel et al.).
Catheters are also known in the medical field for sensing and providing feedback data relating to physiological data concerning the patient. For example, U.S. Pat. No. 4,552,127 to Schiff discloses a balloon catheter with a stylet having a distal end coupled to an EKG electrode. The stylet extends through the catheter body to couple the EKG electrode to a proximal end of the catheter body and, thus, to the exterior of the patient's body. U.S. Pat. No. 6,319,242 to Patterson et al. discloses a catheter device with a proximity sensor to alert the user/operator of the location of the distal end of the catheter and its proximity to a stent implanted in a blood vessel wall. U.S. Pat. No. 6,682,508 to Meythaler et al. discloses a central nervous system catheter assembly comprising multiple lumens including a drug delivery branch and a monitoring/sensing branch. The monitoring/sensing branch is adapted for sensing and providing feedback information related to intracranial pressure. U.S. Patent Application Publication No. 2004/0167385 to Rioux et al. discloses a catheter with a sensor adapted to measure one or more physiological parameters associated with the status of a blood vessel, including: pressure, flow rate, temperature, fluid velocity, physical dimensions, vessel compliance, pH saline content, gas content, etc.